It was demonstrated that genomic changes such as loss of heterozygosity (LOH) and hypermethylation of the P1 promoter of the PLAGL1 gene are frequently observed in several types of cancer such as pheochromocytoma [19], ovarian cancer [20], breast cancer [21], pituitary adenomas [22] and hemangioblastoma [23], and in tumor cell lines including breast cancer cell lines [21]. The gene discussed is PLAGL1; the disease is breast carcinoma.